Stretching of cellulose ester yarn



Patented Aug. 24, 1948 STRETflHING F CELLULOSE ESTER YARN Camille Dreyfus, New York, N. Y.

No Drawing. Application October 17, 1944,

1 Serial No. 559,129

Claims.

This invention relates to the production of strong yarns and relates more particularly to the production of strong yarns by stretching yarns having a basis of an organic ester of cellulose of I a relatively low degree of esterification.

' This application is a continuation in part of my application S. No. 453,571, filed August 4, 194-2,

now abandoned.

An object of my invention is the production of strong yarns by stretching yarns having a basis of an organic ester of cellulose of a relatively low degree of esterification.

Another object of my-invention is the production of said strong yarns of regenerated cellulose by the saponification of stretched yarn made from organic esters of cellulose of a relatively low degree of esterification.

Yet another object of my invention is the production of said yarns without the necessity of the use of hot water or steam under high pressure during the stretching operation.

Other objects of my invention will appear from the following detailed description,

Yarns of regenerated cellulose of high tenacity have been produced by the saponification of stretched yarns having a basis of an organic ester of cellulose, such as cellulose acetate. The yarns are stretched during some stage intheir manufacture and the yarns may be increased in length to the extent of 200, 300, 500, or even 1000 or 2000% of their original length. Theyarns acquire a relatively high tenacity on being stretched, which tenacity is retained and in many instances enhanced by saponification. Th resulting high tenacity regenerated cellulose yarns are of great I strength and find extensive employment where yarns of .an unusual degree of strength are desired.

The cellulose acetate, or other organic ester of cellulose, yarn is usually stretched whenit is in a somewhat, softened condition. This condition may be obtained by the use of troublesome volatile solvents, latent solvents, or swelling agents for the organic ester of cellulose. When yarn of ordinary cellulose acetate of commerce (of say 53 to 56 acetyl value) is stretched to a high degree, the best method is to use hot water or wet steam as the softening agent. However, in order to enable high degree of stretching to be attained, it is necessary to use temperatures considerably above 100 C. and consequently, the water or wet steam must be maintained at pressures considerably above atmospheric, In order to maintain the pressure, the yarn to be stretched must be introduced into the pressure chamber through many fine orifices, special devices must be used to grad- All these factors entail the expenditure of much labor for both operation and supervision.

I have now discovered that strong yarns of high tenacity may be prepared by stretching yarns of cellulose acetate, or other organic ester of cellulose, of a relatively low degree of esterification without necessity of resorting to the use of hot water or wet steam under any appreciable pressure. In accordance with my invention said strong yarns may be obtained by subjecting yarns having a basis of cellulose acetate of an acetyl value of about to calculated as acetic acid, or other organic ester of cellulose of corresponding low degree of esterification to a stretching operation, while said yarns are subjected to the action of a hot aqueous medium, such as steam or hot water which is at substantially atmospheric pressure. The hot aqueous medium serves to soften said low acetyl yarns and the softened yarns may then be stretched to a substantial degree. Because the use of pressure is obviated, the operation can be carried out by passing the yarn to be stretched through simple open troughs containing the hot water or open tubes containing the steam. As a result, there is no difficulty in running the process and since a vided for each end of yarn being stretched, the

cost of operation and supervision is greatly reduced and the stretching of the yarn maybe combined with another textile operation, such as twisting, during the winding of the yarn.

Stretched yarns prepared in accordanc with my novel process are of high tenacity and may be used as such. Furthermore, the stretched yarn may be saponified to yield regenerated cellulose yarns which likewise possess an unusually high degree of tenacity.

The cellulose acetate, or other organic ester of cellulose, of a relatively low degree of esterification employed is of homogenous character and is soluble in organic liquids. It may be prepared by esterifying cellulose with an esterifying agent such as acetic or other organic acid anhydrid in the presence of a catalyst, for example, sulfuric acid, and a diluent such as acetic acid. The cellulose acetate is then ripened or hydrolyzed to the desired acetyl value in the manner well known in the art. The cellulose may be ripened directly or ripening may be interrupted at some convenient point, the cellulose acetate precipitated and, after washing and stabilizing the ripening may then be continued in the presence of the same or a different ripening agent. The most desirable results are obtained, however, if the cellulose acetate, or other cellulose ester from which the yarns employed in practicing my invention are prepared is ripened or hydrolyzed to the desired solubility characteristics and acyl value in a plurality of stages in'the manner more particularly described in U. S. Patent No. 2,329,701.

The softening of the cellulose acetate, or other cellulose ester, yarns of a relatively low degree of esterification may be carried out conveniently in several ways. The yarn maybe softened by passing it through a trough or bath of water'at or near the boiling point, i. e., at 98 C. to 100 (3.; or, the yarn may be softened by being passed through a. chamber containing steam at or about 100 C. The latter is preferably at atmospheric pressure or maybe at a-pressure very slightly above atmospheric, for example, at a pressure of the order of l lb./sq, in. gauge. The time-required to soften the yarn -so that it may be stretched will vary depending-uponthe tempera- "ture of the aqueous mediumand the degree of esterification of theyarn. Usually, the lower the degree of-esterification, the 'lower willbe the temperature necessary to soften it. 0111 01 aparqticular-temperature, the lower the degreeof esterification the less will be the time necessary for reachingthe-desired degree of softness prior to stretching. Yarns of'heavy denier will naturally require a somewhat longer period of time to soften. Usually the yarns maybe softened sufiiciently when exposed to the action of hot water-or steam' for from'0;2 to' 2.0 seconds. After softeningthe yarns may'be stretched in a continuous manner by being passed from a roll which rotates at a low speed "to one rotating at a higher speed, the roller rotating-at the higher speed servingto give-theyarnthe desired stretch. The degree of stretch may-be varied 'by increas- {ing -or decreasing the differential in theroller speeds. 'The yarn may likewise be stretched in a plurality of stages, For examplapart of the stretch may be imparted to the yarn'by softening and'stretching in one stage and the remainder of-the stretch may be imparted by a second sof- -or-more times their original length.

After being collected on bobbins or the like the warns may be saponified while in package form by batch processes. In lieu of employing a-batch process for saponification, however, the yarns -may be saponified in a continuous-manner. This -may be done conveniently by leading the stretched yarns directly into a saponifying bath, the path through the saponifyingbathbeing of sufiicient length so that the yarn is completely saponified before leaving the bath. After sa- :ponification the yarn is washed free ofthe saponifying agent, dried and'wound into packages of convenientsize.

The saponification may becarried out-by means of any suitable 'basic agent. The saponifying agent maybe inorganic in nature such as, for example, sodium hydroxide, potassium hydroxide, sodium silicate, ammonium'hydroxide, sodi- :Llm. carbonate, or other inorganic basic agent.

Organic saponif'ying agents may also be em ployed such as, for example, methyl amine, ethylene diamine, triethanolamine or other organic bases. The saponifying agents may be employed in varying concentrations in aqueous, alcoholic or aqueous-alcoholic solutions. The sa'ponifying bath may be at a temperature of 20 to 100 C. For example, when aqueous solutions of sodium hydroxide are employed, they :may be of concentration of 0:1 to 5% by weight and saponification may be effected in from 30 to 180 minutes with the solution at 30 to 90 C. When employing aqueous solutions of sodium hydroxide as the saponifying medium, it is preferable to include a buffer salt such as sodium chloride or sodium acetate in said solution. Suitable methods which may be employed for saponification of the stretched yarns are more particularly described in U. S. Patent No. 2,053,766.

In Order further to illustrate my invention but without being -limited thereto, the following examples are given:

Example I perature :with a reducedamount of sulfuric :acid

present during ripeningasmoreparticularly described .in U. S. Patent No. 2,329,706. Theyarn is passed through a trough 23 to 40 inches in length containing water at 9.9-1000. The-softened yarn is passed to stretching rollers and stretched to v1.0 times its original length. the speed of travel :of the yarn at .the stretching being :50 to 60 meters per minute. The stretched yarn is passed to=a :winding apparatus where {twist may be inserted during winding. This stretched yarn has -;a high tenacity. The stretched yarn m y be saponi-fied in a saponification bath which comprises a 0.6% aqueous solution .of sodium hydroxide in a 10% solutionof sodium acetate.

The bath is'maintained at 40 to 45C. for one hour and isthen raised to 80 1C.-and held ,atithis temperature for hour whenisaponificationds completed. The stretched, saponi-fied yarn is -;of every high tenacity.

Example II Cellulose acetate of an acetyl value of 40.9%, calculated as acetic acid, is dry "spun'into a yarn of 480 denierhavingBO filaments from an 80/20 acetone/water solution of a concentration of about 23%. The cellulose acetate employed is -prepared in a manner similar to that described in Example I. The yarn is passed through=a chamber containing steam, free of organic solvents at anatmosphericpressure of or at a slight pressure about '1 1b./sq. inch gauge, the arrangement being such that the yarn is exposed to the action of the-steam for about 0.2second. The softened yarn is passed to stretching rollers and stretched continuously to I000% of its original length. The-stretched yarn is wound on bobbins and saponified in a man-nerdescribed in Example I.

It is to be understood that the 'foregoingdetailed description is given merely by way of illustrationand that many variations-may be'mde therein without departing from the spirit of my invention.

Having described my invention, What I desire to secure by Letters Patent is:

1. Process for the production of strong filaments, threads, yarns and like textile materials, which comprises subjecting filaments, threads, yarns and like textile materials, having a basis of an organic ester of cellulose ripened in its primary solution to an acyl value equivalent to that of a cellulose acetate having an acetyl value of 40 to 45%, calculated as acetic acid, to the action of a hot aqueous fluid medium at substantially atmospheric pressure, until they are softened, and imparting a substantial degree :of stretch of at least 5 times to said softened textile material to increase the tenacity thereof.

2. Process for the production of strong filaments, threads, yarns and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of a hot aqueous fluid medium at substantially atmospheric pressure, until they are softened, and imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof.

3. Process for the production of strong fllaments, threads, yarns and like textile materials, which comprises subjectin filaments, threads, yarns, and like textile materials, having a basis of an organic ester of cellulose ripened in its primary solution to an acyl value equivalent to that of cellulose acetate of an acetyl value of 40 to 45%, calculated as acetic acid, to the action of a hot aqueous fluid medium at substantially atmospheric pressure, until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material.

4. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of a hot aqueous fluid medium at substantially atmospheric pressure, until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material.

5. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of a hot aqueous fluid medium at substantially atmospheric pressure at a temperature of about 100 C., until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material.

6. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of hot Water at substantially atmospheric pressure at a temperature 6 of about C., until they are softened, and irnparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof.

'7. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of hot water free of organic solvents for said cellulose acetate at a temperature of 98 to 100 C. and at substantially atmospheric pressure, until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material.

8. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of steam at substantially atmospheric pressure, until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material.

9. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of steam at a pressure of about one pound per square inch gauge, until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material,

10. Process for the production of strong filaments, threads, yarns, and like textile materials, which comprises subjecting filaments, threads, yarns, and like textile materials, having a basis of cellulose acetate ripened in its primary solution to an acetyl value of 40 to 45%, calculated as acetic acid, to the action of hot water at atmospheric pressure and at a temperature of 98 to 100 C., until they are softened, imparting a substantial degree of stretch of at least 5 times to said softened textile material to increase the tenacity thereof, and saponifying the textile material with an aqueous solution of a basis saponifyin agent.

CAMILLE DREYFUS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,144,633 Moncrieff et al. Jan. 24, 1939 2,053,767 Dreyfus Sept. 8, 1936 2,198,660 Dreyfus (2) Apr. 30, 1940 FOREIGN PATENTS Number Country Date 312,096 Great Britain (1) May 17, 1929 340,436 Great Britain (2) Jan. 1, 1931 438,584 Great Britain (3) Nov. 12, 1935 438,586 Great Britain (4) "Nov. 13, 1935 

